The Decent Way To Reboot Frozen Kernels.

1. First, the option within the kernel needs to be turned on.
   1. sudo sh -c “echo \”1\“ > /proc/sys/kernel/sysrq”
2. Then; the sequence R .. E .. K .. S .. U .. B can be typed slowly while holding ALT + SysRq

Following are the command keys available for Alt+SysRq+commandkey.¹⁾

• ‘k’ – Kills all the process running on the current virtual console.
• ’s’ – This will attempt to sync all the mounted file system.
• ‘b’ – Immediately reboot the system, without unmounting partitions or syncing.
• ‘e’ – Sends SIGTERM to all process except init.
• ‘m’ – Output current memory information to the console.
• ‘i’ – Send the SIGKILL signal to all processes except init
• ‘r’ – Switch the keyboard from raw mode (the mode used by programs such as X11), to XLATE mode.
• ’s’ – sync all mounted file system.
• ‘t’ – Output a list of current tasks and their information to the console.
• ‘u’ – Remount all mounted filesystems in readonly mode.
• ‘o’ – Shutdown the system immediately.
• ‘p’ – Print the current registers and flags to the console.
• ‘0-9′ – Sets the console log level, controlling which kernel messages will be printed to your console.
• ‘f’ – Will call oom_kill to kill process which takes more memory.
• ‘h’ – Used to display the help. But any other keys than the above listed will print help.